gistfile1.txt

#/bin/bash

curl -I localhost:6081 -H "Cookie: client1"
curl -I localhost:6081 -H "Cookie: client2"
curl -I localhost:6081 -H "Cookie: client1"
curl -I localhost:6081 -H "Cookie: client4"
curl -I localhost:6081 -H "Cookie: client2"
curl -I localhost:6081 -H "Cookie: client1"
curl -I localhost:6081 -H "Cookie: client1"
curl -I localhost:6081 -H "Cookie: client2"
curl -I localhost:6081 -H "Cookie: client1"
curl -I localhost:6081 -H "Cookie: client4"
curl -I localhost:6081 -H "Cookie: client2"
curl -I localhost:6081 -H "Cookie: client1"

Sticky hashing

vcl 4.1;

import cookieplus;
import header;
import std;
import directors;

backend default {
        .host = "127.0.0.1";
        .port = "8081";
}

backend s2 {
        .host = "127.0.0.1";
        .port = "8082";
}

sub vcl_init {
        new cdir = directors.hash();
        cdir.add_backend(default,1);
        cdir.add_backend(s2,1);
}

sub vcl_recv {
        cookieplus.parse(req.http.cookie);
        set req.backend_hint = cdir.backend(req.http.Cookie);

        set req.http.x-backend = req.backend_hint;
        #we return(pass) to prove it "sticks", run regular hash in a real setup instead
        return (pass);
}

sub vcl_backend_response {
        #PLACEHOLDER
        # we add Set-Cookie handling is backends do not set them
}
sub vcl_deliver {
        set resp.http.x-cookie = req.http.Cookie;
        set resp.http.x-backend = req.http.x-backend;

        # we now unset a bunch of resp headers to make the response easier to read
        # do not do on real setups.
        unset resp.http.Server;
        unset resp.http.Date;
        unset resp.http.Content-Type;
        unset resp.http.Content-Length;
        unset resp.http.X-Varnish;
        unset resp.http.Age;
        unset resp.http.Via;
}